The development of electrochemical techniques for in situ brain measurement in laboratory animals is very impoetant to the on-going research in psychopharmacologic and behavioral science, especially those related to monoamine neurotransmitters. The main goal of this study is to optimize the measurement system for more accurate and more selective determinations of the absolute brain extracellular concentrations of the species of interest. This will be done via modifying of the micro graphite electrode surface for achieving the necessary separation for ascorbic acid and dopamine, via optimizing the experimental parameters for reducing the depletion of the detectable species near the electrode tip in brain tissue, and via developing a new microprocessor aided measurement scheme, termed multiple step chronoamperometry, for accurate and selective determinations of ascorbic acid, monoamine neurotransmitters, serotonins and "methoxylated" metabolites. Amphetamine stimulations will be used as a model system, but new information is expected from this study because of the capability of the measurement system. The underlined purpose is to refine the in vivo electrochemical techniques for monitoring brain chemical activities in experiments associated with complex behavioral changes.